memory fragmentation issues in 1.2?

George Schlossnagle george at
Wed Dec 6 22:44:52 UTC 2006

Paul T wrote:
> Turn off the OOM killer and see what happens?

I could.  I would expect it to actually OOM and die when it exceeds
addressable memory space.

> If you are running Linux, you might be surprised with
> the behaviour of it's memory manager on memcached node
> dedicated to memcached.

To be clear, I'm not seeing a performance issue, as I'm not actively
swapping (even when my RSS exceeds phys mem), I'm seeing a loss of
addressable memory issue, which is both generally troubling and
eventually terminal.

Memory fragmentation isn't a myth.  I can create you an app quite easily
that does not leak memory but will eventually run out of addressable
memory space and eventually fail in malloc.  I'm happy for that not to
be the case here, but that behavior is certainly realizable (and I've
seen it and had to work around it in large commercial server
applications as well - so it's not academic either).


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